1. Field of the Invention
The invention relates to a motor vehicle lock with an electrical opening drive.
2. Description of Related Art
First of all, in general, motor vehicle locks basically have a lock mechanism by which the motor vehicle lock is to be switched into various operating states, for example, into the operating states double lock (DL), child safety (CS), center lock (CL) and unlock (UL) In the operating state UL, the door can be opened by actuating the inside door handle and the outside door handle. In the operating state CL, it is not possible to open from the outside, but it can be opened from the inside. In the operating state CS, it is possible to open the door from the outside, but not from the inside. In the operating state DL, it is not possible to open the door from either the outside or from the inside, so that, even when the window is smashed, the motor vehicle door cannot be opened.
Motor vehicle locks of the type under consideration are often equipped with an electric opening drive. Use of such locks began for rear hatch locks and rear door locks, but such use has since been expanded to motor vehicle side door locks which have a so-called OBW (open by wire) drive (electric motorized opening aid). These motor vehicle locks are acquiring great importance especially in conjunction with a passive entry system.
Basically, work has been underway for a long time on motor vehicle locks which operate exclusively electrically, i.e., they no longer have a lock mechanism. In terms of the basic principle, these motor vehicle locks have been known since the 1970's. They have only latches and ratchets and the electric motorized opening drive is for the ratchet (rotary drive, linear drive, solenoid, etc). All operating states are implemented exclusively electronically by the control electronics which clears or blocks access to the electrical opening drive.
Safety engineering considerations, as before, result in the fact that motor vehicle locks with an electrical opening drive are not made as purely electrical locks, and at least for key functions, have a mechanical redundancy. Then, there is at least another lock mechanism by which individual functions can also be mechanically triggered in any case in an emergency.
On the one hand, it is desirable for the motor vehicle lock to have a structure which is as simple as possible; this would militate in favor of a pure electric lock. On the other hand, safety engineering requirements must be met; this requires a lock mechanism and furthermore, entails the necessity of also being able to trigger the various operating states mechanically and electromechanically.
In individual cases, to trigger all functions including the electrical opening drive, three electric motorized drives are necessary, specifically an electromechanical central locking drive (for UL and CL), an electromechanical double lock drive (for DL and CS), and the electrical opening drive. It can be imagined what costs such a motor vehicle lock would engender.
Therefore, efforts are being directed at making do with as small a number of electric drives as possible, in spite of performing all functions and in spite of implementing sufficient mechanical redundancy. In addition, there is the desire to have to use as few microswitches or proximity electronic switches as possible for controlling the electric drive motors. Accordingly, it is preferred to have the operating states achieved as much as possible by blocking operations. In a blocking operation, the drive element which is driven by the electric drive motor runs against a more or less stationary stop. By monitoring the torque, preferably by current monitoring of the electric drive motor and/or by a timing circuit, then the electric drive motor is turned off in a quite specific position. Generally, resetting of the electric drive motor into a neutral position will preferably take place. However, resetting need not be approached especially accurately, it can even be accomplished mechanically by spring force resetting. With control of the electric drive motor in a blocking operation, at the same, time temperature-induced fluctuations are avoided in the position of the drive element which result in inevitable overtravel of the electric drive motor after being turned off by means of a switch.
One interesting step in the above explained development trend has already been made (European Patent EP 1 113 133 B1). In the motor vehicle lock there, from which the invention proceeds, the second function of the electrical opening drive is a child safety function. However, there is the problem that the child safety function can only be turned on by moving the drive element in the second direction of motion because the first direction of motion is “reserved” for the opening drive function. This problem is solved in the above explained design of a motor vehicle lock by a type of “ballpoint pen mechanism” of the child safety actuation. The second function is turned off in the same direction with turning-on in turn against a resetting spring force. This design is imaginative, but requires complex additional mechanical engineering in the form of the ballpoint pen mechanism.
Another approach consists in working with a “floating” blocking stop (European Patent EP 1 061 212 B1). The floating blocking stop results in the desired stop for implementing block operation for turning off the electric drive in the intermediate position. In this way, the turn-off position can be defined at almost any location which can be established beforehand, without using a switch. Implementation of an additional floating blocking stop is, of course, complex in mechanical-construction terms.
Finally, U.S. Pat. No. 6,557,387 (commonly owned) describes an especially feasible electric motorized actuator for a motor vehicle lock and the contents of this patent are hereby incorporated by reference into this application. With this actuator not only can operating states CL and UL of a motor vehicle lock be implemented, but also the operating state DL in any case. For this, a certain feasible control crank which has a catch is implemented, the double lock lever being kept in the operating state CL by latching after mechanical-manual shifting from the operating state DL into the operating state CL.